Characterisation of friction and lubrication regimes in premium tubular connections

A friction test rig has been developed to carry out repeated sliding friction tests for premium tubular connections. The test rig enables accurate measurement of friction in various contact regimes which are relevant to the threaded connections between tubular components. Higher load tests can simulate the contact in metal-to-metal seals under very high contact pressures by using perpendicular pin-on-pin tests. The contact in the thread loading flank under intermediate pressures can be simulated by using larger radius coupon-on-coupon tests. The measured coefficient of friction is well correlated with a lubrication parameter combining lubricant film thickness and initial surface roughness.

► A cross-cylinder friction test rig has been developed to simulate threaded tubular connections.
► Test results reveal the effects of surface treatment, burnishing and speed on friction.
► Analysis of lubricant film thickness using Hamrock and Dowson theory infers ‘mixed’ regime.
► The coefficient of friction is well correlated with a lubrication regime parameter Λ.